Early Earth Not So Hellish, New Study Suggests

The prevailing view of early Earth is that it was utter hell, a fiery environment
unsuitable for life. Scientist even named it the Hadean eon, for the ancient
Greek word for the down under.

But the planet may have been suitable for life just 200 million years after
the solar system formed, new research suggests.

This new view "contrasts with the hot, violent environment envisioned
for our young planet by most researchers and opens up the possibility that life
got a very early foothold," Bruce Watson of Rensselaer Polytechnic Institute
said today.

Prevailing view

Earth formed about 4.5 billion years ago, just after the Sun collapsed into
being. After formation, planets are thought to take some time to fully contract
and cool.

Image
Gallery

The
Fury
of Volcanoes

The popular belief among scientists is that Earth during the Hadean eon - all
Earth time prior to 3.8 billion years ago - was a hot, volcanic
environment in which no living thing could survive. Of course nobody was there
to take pictures, either, so it's all theory.

Watson claims there were oceans and continental crust similar to what we have
today.

"Our data support recent theories that Earth began a pattern of crust
formation, erosion, and sediment recycling as early in its evolution as 4.35
billion years ago," he said.

Even with the existence of water and crust, the Earth
was not the friendly place we now know. The planet would still have been quite
hot, and the atmosphere would have consisted only of carbon dioxide, water,
and volcanic gases. But life may still have been able to exist in these types
of conditions. After all, scientists today find bacteria and other microbes
living in similarly hostile
conditions.

Nobody knows when
or how life began, however. It may have developed just once, or as some
scientists have theorized, the planet may have been sterilized by asteroid bombardments
one or more times, with life springing forth twice or even several times.

"I think the picture we've
helped to bring into focus is that complex biomolecules (and possibly life itself)
may well have gotten started very early in the history of our planet,"
Watson told LiveScience. "Previously, the widely accepted idea has
been that 'impact
sterilization' prevented life from getting a foothold until much later."

The findings are published in the May 6 issue of
the journal Science.

Looking back in time

Watson and his colleague, Mark Harrison of Australian National University,
developed a technique for looking at zircon crystals to determine the temperature
and possible environmental conditions of early Earth.

"Zircon allows us to go further back in geologic time because they survive
processes that rocks do not," said Watson. The zircon crystals they studied
predate the world's oldest rocks by 400 million years.

"Although they measure only a fraction of a millimeter in size, zircons
hold a wealth of information about the very earliest history of Earth,"
he said.

Watson and Harrison measured the titanium content of the crystals from the
Jack Hills area of Western Australia. From this data, they could determine the
zircon's crystallization temperature. The temperature data they uncovered supports
the existence of a wet Earth within 200 million years of the solar system's
formation.

"Zircons are extremely durable physically," Watson explained. "They
can get bounced around in stream beds without getting ground to dust. More importantly,
however, they are amazingly resistant to chemical attack -- acids, supercritical
water, and even molten rock [magma] can't dissolve them under most circumstances."

Sun, sand, surf

What might early Earth have looked like? Watson's colleague Mark Harrison,
a geochemist at UCLA, suggests picturing a sandy beach near sparkling blue water
with a blue sky above ... and lots of volcanoes.

"Well, I can't personally say that we really know that," Watson
cautioned. "But, yes, there almost certainly were lots of volcanoes --
probably many more than today -- and enough water to sustain rivers and oceans."

He notes that this is just an inference, however, based on a reading of the
minerals in the zircons.

Bjorn Carey

Bjorn Carey is the science information officer at Stanford University. He has written and edited for various news outlets, including Live Science's Life's Little Mysteries, Space.com and Popular Science. When it comes to reporting on and explaining wacky science and weird news, Bjorn is your guy. He currently lives in the San Francisco Bay Area with his beautiful son and wife.